DNA’s half-life identified using fossil bones

October 10, 2012

A study of bones from extinct birds suggests the double helix too has a measurable half-life — and that we have underestimated its ability to survive in the fossil record, New Scientist reports.

Part of the reason a DNA half-life has been so elusive is that it is hard to find a large enough cache of samples that have been exposed to similar conditions. The moa bones they used were all between 600 and 8000 years old, and came from a 5-kilometer-wide area of New Zealand’s South Island, key factors for helping identify a regular pattern of decay.

With an estimated burial temperature of 13 ºC, the DNA’s half-life was 521 years — almost 400 times longer than expected from lab experiments at similar temperatures, says Allentoft.

Half-life of 158,000 years

The oldest DNA to date belongs to insects and plants and was found in 450,000 to 800,000-year-old ice. Under subzero conditions, Allentoft and Bunce estimate that DNA’s half-life can be up to 158,000 years, meaning the last remnants would disappear around the 6.8-million-year mark. Allentoft does say that is an optimistic assessment, and doesn’t imply that samples of DNA large enough to measure could be extracted from such old bones.

DNA or other stable chemical compound “half-life” seems an odd concept to me. Obviously any complex molecule is likely to break down some time – cosmic rays, temperature change, etc. But on the other hand, until such event, stable means stable. I also thought the idea for reconstructing dinosaur, etc., DNA was based on analyzing and “reassembling” many billions of very small molecular fragments … a biostatistical exercise … of which there should be plenty to be found in an intact dinosaur skeleton, one would think. That, after all, was the original way the human genome was sequenced and reconstructed, wasn’t it?